Activists say Syrian forces have dropped a crude bomb on a mosque in a rebel-held neighborhood of the northern city of Aleppo, killing at least five people, including children.

Activist Hassoun Abu Faisal of the Aleppo Media Center says the mosque in the Masaken Hanano area was also used as a school and that children were inside when it was hit on Tuesday with a barrel bomb — a crude device packed with fuel and scraps of metal.

The Local Coordinating Committees, another activist group, says five people were killed. It wasn’t immediately clear how many were children.

President Bashar Assad’s troops have pounded opposition areas of the divided city since mid-December, intensifying their efforts to seize rebel-held parts of Aleppo. Hundreds of civilians have been killed in the bombings.